Someone who is insecure about their penis size and continuously asks for the size of his peers penis, for comparison. Typically, a Robby Brann is white, and will lie about the size of his own penis to avoid insult. He is an annoyance to a friend group and a disgrace to mankind.
Robby Brann: Hey dude, how long is your shlong?
Black friend who doesn't give a shit: Twelve inches.
Robby Brann: Yeah man, me too. I got that five dollah' footlong.
Black friend who doesn't give a shit: Go fuck yourself you lying piece of shit. White niqqa fuck.